574 NERVOUS SYSTEM. 



Tactile Corpuscles. The name tactile corpuscles implies that these bodies are con- 

 nected with the sense of touch ; and this view is sustained by the fact that they are 

 found almost exclusively in parts endowed to a marked degree with tactile sensibility. 

 They are sometimes called the corpuscles of Meissner and Wagner, after the anatomists 

 by whom they were first described. The true tactile corpuscles are found in greatest 

 number on the palmar surfaces of the hands and fingers and the plantar surfaces of the 

 feet and toes. They exist, also, in the skin on the backs of the hands and feet, the nip- 

 ples, and a few on the anterior surface of the forearm. As we shall see when we come 

 to describe them fully, they are situated in the substance of the papillae of the skin, and 

 they cannot fail to have an important function in connection with the sense of touch. 



We have already treated of the general structure of the skin and have seen that the 

 largest papillae, measuring from ^ to -fa of an inch in length, are found on the hands, 

 feet, and nipples, precisely where the tactile corpuscles are most abundant. Corpuscles do 

 not exist in all papilla3, and they are found chiefly in those called compound. In a space 

 of about 7 V of an inch square on the third phalanx of the index-finger, Meissner counted 

 four hundred papilla?, in one hundred and eight of which he found tactile corpuscles, or 



FIG. 179. Papillce of the skin of the palm of the hand. (Sappey.) 



1, papilla with two vascular loops ; 2, papilla with a tactile corpuscle ; 3, papilla with three vascular loops ; 4, 5, large 

 compound papillae ; 6, 6, vascular net-work beneath the papilhe ; 7, 7, 7, 7, vascular loops in the papilla? ; 8, 8, 8, 8, 

 nerves beneath the papilte ; 9, 9, 10, 11, tactile corpuscles. 



about one in four. In the same space on the second phalanx, he found forty corpuscles ; 

 on the first phalanx, fifteen ; eight on the skin of the hypothenar eminence ; thirty-four 

 on the plantar surface of the ungual phalanx of the great-toe ; and seven or eight in the 

 skin on the middle of the sole of the foot. In the skin of the forearm, the corpuscles are 

 very rare. Kolliker states, also, that the tactile corpuscles usually occupy special papillae, 

 which are not provided with blood-vessels ; so that the papilla of the hand may be 

 properly divided into vascular and nervous. 



The form of the tactile corpuscles is oblong, with their long diameter in the direction 

 of the papillae. Their length is from ^ to ^ of an inch. In the palm of the hand, 

 they are from -^ to -j-i^ of an inch long, and from -^ to -^ of an inch in thickness. 

 They are generally situated at the summits of the secondary eminences of the compound 

 papillae. According to Kolliker, the tactile corpuscles consist of a central bulb of homo- 

 geneous or slightly-granular connective-tissue substance, analogous to the central bulb 

 of the Pacinian corpuscles, and a covering. Treated with acetic acid, the covering pre- 

 sents numerous elongated nuclei arranged in a circular manner, which he believes to be 

 nuclei of connective tissue, and a few fine elastic fibres. One, two, and sometimes three 

 or four dark-bordered nerve-fibres pass from the subcutaneous nervous plexus to the 

 base of each corpuscle. These surround the corpuscle with two or three spiral turns, 

 and they terminate by pale extremities at the surface of the central bulb. This arrange- 

 ment is shown in Fig. 180. 



